We request funds to purchase a supercontinuum STED microscope. The STED (STimulated Emission Depletion) microscope, invented by Stefan Hell, is the first light microscope to break the Abbi diffraction limit. Abbi's barrier, a fundamental law of physics, states that an infinitesimally small source of light, e.g. a single fluorescing 1 nm molecule, cannot be imaged to a spot much smaller than roughly 300 nm wide, because photons spread out as they pass by an edge. Thus, any structure smaller in size will appear as a diffraction- limited blurred spot. Since many structures of biological interest are on a smaller scale, this is a crippling limitation to light microscopy. Stefan Hell (Max-Planck Institute for Biophysical Chemistry, Gvttingen) solved the problem of the optical diffraction limit with the STED microscope. With this technique, he has demonstrated a roughly ten-fold increase in XY resolution, an advance that opens a huge window of opportunity for studies in the medical and biological sciences that heretofore have been impossible. We believe that we are uniquely suited to acquire this new STED microscope. We are a group of 12 experienced, independently-funded researchers with expertise in neurobiology, cell biology, molecular biology, as well as advanced optical technologies. We have established a close working relationship with S. Hell who has agreed to serve as a Senior Consultant. Restrepo (PI) worked with him in Gvttingen on a project published in PNAS. In addition, Betz, a Major User, trained a key colleague of S. Hell's, Silvio Rizzoli (PhD, University of Colorado, 2004), former postdoc with Dr. Hell, now Group Leader (Assistant Professor equivalent) at the European Neuroscience Institute, Gvttingen. Rizzoli has agreed to serve as Technical Consultant. Emily Gibson (Co-PI) and Tim Lei a Technical Consultant at CU Denver are both experienced in nonlinear laser optics. Gibson will visit S. Hell's lab in Gvttingen to be trained on the implementation of the supercontinuum STED. All our Users are NIH-funded investigators. The focus of all projects is in basic biological and disease related research. Each proposed project outlined in this application is high impact research that will advance current scientific understanding. These projects cannot be accomplished with any other instrument currently available to us. The STED microscope will be incorporated into the existing core Light Microscopy Facility (LMF) at the University of Colorado Denver. For six years, the LMF has served the needs of more than 2000 faculty, staff, and trainees, currently with four advanced fluorescence microscopes. Experienced and knowledgeable LMF personnel determine time allocation and user fees, attract and train new users, insure security, and manage billing and a friendly online scheduler. When a new instrument is installed, special start-up activities insure its smooth incorporation into the LMF.